1. Field of the Invention
The invention related to a base body of a headrest of a vehicle seat having,                a base, particularly for receiving headrest carriers for disposing the headrest on a vehicle seat, and        a support body having a support surface for a head.        
2. Description of the Related Art
Base bodies of the initially named type as well as headrests produced from them are well known from the prior art. Along with a comfort function in normal vehicle operation, headrests further also satisfy a safety function. The safety function is to avoid or to reduce cervical vertebrae injuries, especially the risk of frequently occurring whiplash due to a hyperextension and overstressing of the cervical spine and supporting muscles. The injuries resulting from the lash effect are also known by the term “whiplash”.
Along with a hyperextension of the cervical spine, caused by the backward head motion in the case of a rear collision, the further danger exists that the head, lying against the headrest in the course of the accident, after attaining a maximum of an also occurring rearward displacement of the seatback, is accelerated again by the headrest in the direction towards the front of the vehicle. This so-called head rebound velocity (HRV) effect, that is, the negative acceleration effect, involves the danger of a cervical spine injury, in addition to the whiplash effect.
To avoid injuries to the cervical spine, already so-called crash active headrests are disclosed in which during normal driving operation the distance between the head and the headrest is relatively large in comparison to conventional, inactive headrests. In the case of a rear collision, the headrest undergoes a sensor controlled displacement in the drive direction, i.e. in the direction of the head. As a result, the distance between the headrest and the head is reduced which then avoids a hyperextension of the cervical spine. The vehicle manufacturer's changed design specifications which intend a reduction of the distance between the headrest and the head in normal driving operation, largely limit the application area of such active headrests which require a minimum distance, such that alternative solutions are necessary.